There are a number of diseases and conditions in the middle ear that cause hearing loss in both children and adults. In children it is particularly important to expedite interventions to restore hearing since it negatively impacts language development and academic performance. An example is cholesteatoma, a benign lesion due to abnormal skin growth in the middle ear which facilitates erosion of bone, including the ossicles, causing permanent damage. The preferred surgical approach comes with a relatively high risk of both recurrent and residual lesions (~10%). While the initial diagnosis is typically straight forward because of the size of the lesion when the patient seeks medical care, identifying residual cholesteatoma after the initial resection has been performed is difficult even using advanced MRI and CT techniques. Consequently, ?second look? surgeries are frequently preformed to verify that the middle ear is lesion free. An imaging solution able to identify cholesteatoma lesions in the clinic could substantially reduce the number of second look surgeries and their associated costs and potential co-morbidities (e.g. sensorineural hearing loss, vertigo and surgical trauma to the facial nerve). Disruption of the ossicular chain due to cholesteatoma or other etiologies (e.g. trauma, chronic otitis media, osteosclerosis) is commonly treated with ossicular replacement surgery to restore hearing. Unfortunately, the outcomes vary greatly. While the variation is not entirely understood, an accepted contributing factor is the choice of the length of the prostheses with loose fitting prostheses performing significantly better than tight fitting prostheses. However, there is currently no imaging technology that can provide pre- or intra-surgical quantitative guidance on optimal prosthetic length. Scar tissue formation around the prosthesis can also adversely affect hearing outcomes, and there is no reliable way to identify this problem. Therefore, if the outcome is poor it is often difficult to determine the cause and whether a revision surgery is indicated. Advanced optical imaging tools based on Optical Coherence Tomography (OCT) can largely fill this gap in imaging technology thus providing improved diagnostics, leading to better outcomes and lower health care costs. OCT has both the spatial and temporal resolution to measure the morphological features and the function of the ear. The challenge with utilizing OCT for interrogating the middle ear space is access. OCT can penetrate roughly 2 mm into tissue, hence access to the middle ear for imaging must be made via the ear canal or Eustachian tube. The technology development proposed here is directed at overcoming the access issue and enabling comprehensive functional and morphological imaging of the middle ear space. A set of pilot studies will address validation of our approach for specific pathologies where we believe an imaging solution can swiftly impact clinical care.